As a process for producing a dipeptide wherein two L-amino acids are linked by α-bond, a process utilizing a ywfE gene product which is one of the synthases of bacilysin, a dipeptide antibiotic derived from a microorganism belonging to the genus Bacillus, is known (patent documents 1-8).
As a method of improving a producing ability of a strain in L-amino acid fermentation, a method including altering an efflux system for L-amino acid in a microbial cell is known (patent documents 9-14). In addition, the presence of an efflux system for Microcin J25, a peptidic antibiotic, is also known (non-patent document 1).
Also in the production of a dipeptide, dipeptide productivity is considered to be improved by enhancing the activity of a dipeptide exporting system, namely, a protein having an activity to transport a dipeptide in the microbial cell to the outside of the microbial cells (hereinafter to be referred to as a dipeptide transporting activity). However, a protein having a dipeptide transporting activity has not been reported heretofore.
It is known that bcr gene of Escherichia coli is a gene encoding membrane protein which relates to bicyclomycin resistance (non-patent document 2), and norE gene is a gene encoding an efflux pump which relates to quinolone resistance (non-patent document 3). emrD gene has been reported as a gene encoding an SDS transporting protein (non-patent document 4). ydeE gene is predicted to be a gene encoding a drug transporting protein, but its activity has not been confirmed (non-patent document 4). The function of yeeO gene is completely unknown.    patent document 1: WO 2004/058960    patent document 2: WO 2005/045006    patent document 3: WO 2005/052153    patent document 4: WO 2005/052177    patent document 5: WO 2005/103260    patent document 6: WO 2006/001379    patent document 7: WO 2006/001381    patent document 8: WO 2006/001382    patent document 9: WO 97/23597 A2    patent document 10: US 2003/0113899 A1    patent document 11: JP-A-2000-116390    patent document 12: JP-A-2000-189177    patent document 13: JP-A-2005-287333    patent document 14: JP-A-2005-237379    non-patent document 1: J. Bacteriol., 187, 3465-3470 (2005)    non-patent document 2: Gene, 127, 117-120 (1993)    non-patent document 3: J. Antimicrob. Chemother., 51, 545-56 (2003)    non-patent document 4: J. Bacteriol., 183, 5803-5812 (2001)